As an important raw material for the production of ammonia, methanol, and liquid hydrocarbons, hydrogen is mainly produced through catalytic steam reforming of methane, which is strongly endothermic and requires high temperature (e.g., about 700° C. to about 900° C.) to achieve maximum conversion to H2, CO, and CO2 at high pressure (e.g., about 20 bar to about 40 bar). High purity hydrogen can then be directly obtained via a separation step such as hydrogen permeation through a proton-conducting membrane under a pressure gradient at high temperature. The application of membrane technology is expected to considerably reduce the capital and energy cost in hydrogen production. Composite membranes consisting of BaCeO3-based proton conductor and electronic conductor (e.g. nickel) have been developed for this application. However, these membranes (e.g. Ni—BaZr0.8-xCexY0.2O3-δ (Ni—BZCY), 0.4≦x≦0.8) suffered serious performance loss in CO2-containing environment at 900° C. due to reaction between BaCeO3 and CO2. U.S. Pat. No. 6,569,226 B1 issued to Doors et al. on May 27, 2004 discloses a hydrogen permeable composite membrane based on hydrogen transporting metal and a non-proton-conducting ceramic, such as ZrO2, Al2O3, BaTiO3, and SrTiO3. These ceramics only contribute to the mechanical strength of the composite membrane but not the hydrogen permeability. Among the proton conductors that are tolerant to CO2, BaZr0.8Y0.2O3-δ (BZY)-based materials possesses the highest bulk proton conductivity, and high mechanical strength.